Re: First digital
Welcome to the wonderful world of digital art!
You've got a great start on this southwest scene. I just have a few suggestions as long as you've asked.
First, I'd suggest zooming in to the base of each of the cacti, so yo can get the shadow to meet the bottom of each cacti.
Secondly, I'd think a little about aerial perspective. Colors get a little less intense and cooler as they get further away from us. Making the sand a little less intense (a little lighter or grayer) in the background as it meets the mountains, and I'd also make the purple mountains a little less intense. It will help them to stay in the background.
However, this is a great beginning. I'm not familiar with inkiest, does it let you paint on layers? If so, I'd suggest you do that, because it will be so much easier to work on the mountain again if it is on a different layer.
Painting on layers is a little bit of "thinking differently" but many of can help you with that if you app is capable of it.
Good luck with your painting!